$ { {-3} \times \left[\begin{array}{rrr}{2} & {3} & {-1} \\ {1} & {3} & {1}\end{array}\right] = {?} } $
Solution: To multiply a matrix by a number, multiply each item of the matrix by the number. ${\left[\begin{array}{rrr}{-3}\times{2} & {-3}\times{3} & {-3}\times{-1} \\ {-3}\times{1} & {-3}\times{3} & {-3}\times{1}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rrr}{-6} & {-9} & {3} \\ {-3} & {-9} & {-3}\end{array}\right]}$